Ultrasound imaging is a noninvasive way of investigating with sound waves structures concealed within a body. The generation of the incident sound waves and the reception of their reflections are accomplished with ultrasound transducers, which are usually of piezoelectric material. The transducers produce a burst of ultrasound when excited by a suitable pulse of voltage (say, in the 50-200 volt range for imaging, and in the 5-50 volt range for doppler). It often happens that, owing to the nature of the imaging application, the probe contains a moderate to large number of transducers. In some such applications the number of transducer elements is in the hundreds, the better to achieve a range of spatial perspectives for the object or structure being viewed. In such a case only a subset of the total number of transducer elements is in use at any one time; that subset defines an aperture whose location is moved along the probe in a regular fashion during the imaging process. The conventional way to define the location of the aperture is with a bank of high voltage switches. The high voltage switches connect the transducer elements that are to be the aperture to a collection of transmit and receive circuits in a unit called a scanner. Thus, the notion of a moving aperture for a probe having several hundred transducer elements requires an extensive high voltage switching arrangement, in conjunction with a scanner. The switching arrangement is complex, bulky and expensive; it would be desirable if a simpler way of switching were possible so that the size, complexity and cost of the switching arrangement could be reduced.